1. Field of the Invention
This invention relates to injectable or oral compositions for increasing the growth rate of animals such as swine, cattle, sheep and poultry. The invention also relates to feed compositions containing additives that promote increased growth rates in animals.
2. Prior Art
It is an objective of the meat production industry to stimulate the growth rate of animals. A number of substances have been administered for the purpose of increasing growth rates. For example, it is known that certain compounds having estrogenic activity can be used for this purpose. These compounds, however, sometimes produce serious undesirable side effects.
A variety of other substances are currently being used as animal growth promotants. For promoting growth in swine, for example, quinoxaline compounds can be used, as described by Haddadin et al. (British Patent No. 1,305,138), by R. E. Ivy and R. D. Williams (U.S. Pat. No. 4,128,642) and others. U.S. Pat. No. 3,239,345 to Hodge et al. discloses the use of zearalanol as a growth promoting agent in cattle and sheep. Derivatives of the antibiotic Bacitracin are used as growth-promoting agents in chickens.
With regard to the quinoxalines, antibiotics and their derivatives, the growth stimulating effects of these substances result primarily from the generally improved health status of the animals are not from improved feed conversion. Furthermore, there has been a considerable concern that the widespread use of these compounds for growth promotion may result in the widespread increase in antibiotic-resistant strains of undesirable bacteria through the pressure of natural selection.
Another disadvantage of currently used growth stimulants is that they frequently are active only in limited species, in some cases only in a single animal species.
There is a need for growth-promoting agents which do not have disadvantages associated with prior art growth promotants and which can be used in a variety of species with satisfactory results.